1. Field of the Invention
The present invention relates to a firing mechanism for munition rounds. More particularly, the firing mechanism uses an assembly with a stab firing pin to delay detonation of a munition round after initial contact with a target. The stab firing pin is seated within a supporting disk in a pressure cartridge for proper and reliable firing of the munition warhead.
2. Background Art
The survival of a military unit depends to a great extent on its ability to defeat enemy armor and field fortifications. Substantial improvements in the effectiveness of armor and fortifications to withstand exploding munitions has occurred. Layered defenses and reinforced structures are generally designed to deflect the explosive force of a munition away from a target, or to absorb part of the destructive force as a way to dissipate the damaging effects of the munition. Munitions with a delayed warhead detonation, after target impact, have increased effectiveness in damaging or destroying the target. The delayed timing provides the maximum explosive effect of the munition against the target.
The delayed timing of an exploding munition, after impact, may be required for several reasons. The purpose of the delay is to produce the greatest target effect or efficiency from the warhead. Some munitions penetrate the target without detonating and then function once inside. Other munitions utilize timing between multiple warheads to create the greatest effect against armor. In plastic or squash head warheads, the warhead deforms on target impact and spreads explosive against the target. These warheads must allow a certain amount of deformation to occur before detonating. However, a time delay that is either too rapid or too slow drastically reduces the efficiency of the warhead. Additionally, the reliability of munition detonation must remain extremely high. Detonation reliability in excess of at least 94 percent is normally desired, with detonation reliability in the range of 98 percent or more commonly accepted for weapon use. Additionally pressure cartridges within a munition used to create a timing delay should be able to withstand a certain amount of rough handling.
Three types of methods are commonly used for delaying the initiation of an explosive: chemical or pyrotechnic, mechanical, and electric.
Pyrotechnic delays, generally considered the oldest method, uses a low order burn to initiate or transition a primary explosive into a high order explosion. An example of a pyrotechnic delay is a burning cord used to set off a bomb or stick of dynamite. Pyrotechnic delays are inexpensive although timing accuracy and reliability may not be as high as other methods. Problems arise in trying to make pyrotechnic delays short, such as delays of less than about 1 millisecond. A xc2xd millisecond delay of a pyrotechnic having a low order burn composition comprising Barium Chromate, Boron, and A1A Powder, may require, for example, the pyrotechnic delay to be only about 0.0008 inches long. Such a delay, while theoretically possible, would be near impossible to manufacture. A 2 millisecond delay using a high explosive, such as HNS as a delay medium which has reaction rates much faster than a pyrotechnic delay blend, requires about 13 inches of material length which is generally impractical in most munitions.
Mechanical delays, or clockworks, use a spring mechanism that stabs a detonator to start an explosive reaction. These mechanical timers, however, are unable to provide accurate short delays, such as less than about 10 millisecond. Electronic timers are today""s state of the art, used to set off an electric detonator. Although electronic timers may be constructed to accurately function at extremely short time periods, the size of the circuit and power supply even in the smallest electronic timers may be too large for many applications, In view of the foregoing, there is a need for improvements in the delay timing of cartridges used in exploding munition rounds.
An object of the present invention is to provide a reliable timing delay for the detonation of a munition round.
The present invention includes a fuze explosive train device for detonating a munition, comprising a pressure cartridge having a stab firing pin located adjacent to a gas generator and a stab detonator on the opposite side of the stab firing pin from the gas generator, wherein the stab firing pin is capable of transferring an energy from the gas generator into the stab detonator effective to initiate the stab detonator.
The present invention further includes a method of initiating a stab detonator within a pressure cartridge comprising the steps of providing a device for detonating a munition comprising a pressure cartridge having a stab firing pin located adjacent to a gas generator and a stab detonator on the opposite side of the stab firing pin from the gas generator, wherein the stab firing pin is capable of transferring an energy from the gas generator into the stab detonator effective to initiate the stab detonator; and, causing a chemical reaction that transfers energy from the gas generator onto the stab firing pin, wherein the stab firing pin is forced into the stab detonator effective to initiate the stab detonator.
The present fuze explosive train device uses the successive initiations of the following delays: a pyrotechnic delay, followed by a mechanical delay caused by the rupture of the supporting disk and the transfer of energy across the first gap, a pyrotechnic delay, and then a mechanical delay across the second gap.
The supporting disk is an important part of the fuze explosive train device in that it seats and supports the stab firing pin, and further allows for a controlled mechanical delay upon rupture, which feature is lacking in conventional fuze explosive train devices. The disk is generally flat and circular in shape.
The rupturing of the supporting disk is also an important aspect of the fuze explosive train device as it allows for a very precise control of the mechanical delay, by controlling the material and thickness of the disk.
Yet another important feature of the fuze explosive train device is that the firing pin is freed following the pyrotechnic delay. The stab firing pin of the fuze explosive train device is seated within the supporting disk, and is capable of free movement. In this way, the free movement stab firing pin is not held back by a piston, or significantly affected by the resonance of the piston. As such, the present design achieves an accurate control of the delay mechanism.